Sneaky means acting in a secretive, sly way, often to avoid being noticed or to get away with something. A sneaky person might tiptoe past their sibling's room to avoid being asked to help with chores, or slip an extra cookie from the jar when no one's looking.

The word carries a sense of cleverness mixed with a bit of dishonesty or mischief. A sneaky move in chess catches your opponent off guard. A sneaky plan works because nobody sees it coming. Sometimes sneaky behavior is fairly harmless, like planning a surprise party (which requires sneaking around to keep the secret). Other times it's more troublesome, like a student who finds sneaky ways to avoid responsibilities.

You might call someone a sneak if they regularly act this way, though it's not a compliment. The word suggests someone is being deliberately underhanded rather than straightforward. When your friend asks if you want to play outside and you give them a direct answer, that's honest. But if you pretend you can't hear them while sneaking off to do something else, that's sneaky.

Related words include sly, stealthy, and furtive. All suggest moving or acting quietly to avoid detection, but sneaky specifically implies you're probably up to something you'd rather others not know about.